248 Dry Matter and Nitror/en hi the Potato Tuber 



The average for nine tubers is given in Fig. 3, and Fig. 4 shows the 

 figures obtained for a sample of twenty tubers. 



The tendency for the proportion of nitrogen in the fresh material to 

 decrease from the skin to the inner cortical and then to rise is observable 

 in each zone. There is a distinct increase in nitrogen from the sprout 

 end to the point of attachment in each zone. Thus the increase of dry 

 matter from the terminal to the umbilical region is accompanied by an 

 increase in the percentage of nitrogen in the fresh material. 



Dry Matter Distribution in relation to the structure of the Tuber. 



Figs. 5 and 6 represent respectively transverse and longitudinal 

 sections of the tuber as seen by the naked eye. The vascular bundles 

 stained with phloroglucin show up clearly as a broken ring surrounded 



Fig. 5. Transverse section of potato tulier, 

 natural size. 



Fig. 6. Longitudinal section of 

 potato tuber, natural size. 



by dense-looking tissue. The central translucent part of the tuber with 

 its pith rays penetrating into the outer medullary zone is clearly seen. 

 A section of the tuber magnified eight times is shown in Fig. 7 while 



